Water quality assessment of drinking water has been studied in Zagazig city, El-Sharkia Governorate, Egypt between Summer 2015 to Autumn 2016. Water samples were collected from 7 sites during the four seasons. These sites are raw water (Bahr Mowees), Prechlorinated Water and Postchlorinated Water from Zagazig drinking water treatment plant and 4 drinking water sites which are (Zuhur District, Zagazig university Area, El-Janine street Area, Farouk Street Area). The obtained results clearly indicated that the physical and chemical results agreed with the WHO limit and standard limits for drinking water in Egypt, in Zagazig except alkalinity and residual chlorine. This study indicated the Total viable bacterial counts (T.V.B) on nutrient agar medium, total coliform (T.C.F) and feacal coliform (F.C.F) on endo agar base medium at different sites in Zagazig city through four seasons expressed as colony forming unit (CFU)/100 ml sample of each group using membrane filter technique. In this study 324 isolates were isolated from all sites during different seasons in Zagazig city and purified. It is reported that untreated water sources were more heavily contaminated with both total and faecal coliforms than treated water sources.